This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A346821 #18 Aug 30 2021 21:40:52 %S A346821 1,10,11,101,10111,101101,11101,11101101,1110111,10110111, %T A346821 1011011110111,10110111101101,1110111101101,111011110110111101101, %U A346821 11101111011011110111,101101111011011110111,1011011110110111101111011011110111,10110111101101111011110110111101101,1110111101101111011110110111101101 %N A346821 Lexicographically earliest sequence of distinct terms > 0 such that the concatenation of three successive terms form a palindrome in base 10. %C A346821 This sequence shows only 0's and 1's. The lexicographically earliest sequence of distinct terms > 0 such that the concatenation of two successive terms form a palindrome in base 10 is A000042. %e A346821 a(1) = 1, a(2) = 10, a(3) = 11 form the palindrome 11011 when concatenated; %e A346821 a(2) = 10, a(3) = 11, a(4) = 101 form the palindrome 1011101 when concatenated; %e A346821 a(3) = 11, a(4) = 101, a(5) = 10111 form the palindrome 1110110111 when concatenated; %e A346821 a(4) = 101, a(5) = 10111, a(6) = 101101 form the palindrome 10110111101101 when concatenated; etc. %Y A346821 Cf. A000042. %K A346821 base,nonn %O A346821 1,2 %A A346821 _Eric Angelini_ and _Carole Dubois_, Aug 30 2021